WTPA45 PHFO 211500 TCDCP5 HURRICANE OLAF DISCUSSION NUMBER 27 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP192015 500 AM HST WED OCT 21 2015 THE SATELLITE SIGNATURE OF OLAF CONTINUES TO DEGRADE...WITH THE CLOUD-FILLED EYE SPORADICALLY COMING AND GOING IN CONVENTIONAL INFRARED IMAGERY. DVORAK INTENSITY ESTIMATES CONTINUE TO LOWER...WITH SUBJECTIVE CURRENT INTENSITY ESTIMATES A UNANIMOUS 5.5/102 KT. THE INITIAL INTENSITY FOR THIS ADVISORY IS THEREFORE ESTIMATED TO BE 105 KT...THUS INDICATING THAT OLAF HAS RAPIDLY WEAKENED OVER THE PAST 24 HOURS. THE INITIAL MOTION FOR THIS ADVISORY IS 300/08 KT...WITH A SMALL WARM SPOT ROTATING AROUND THE CENTER SOMEWHAT COMPLICATING THE SHORT TERM MOTION ESTIMATE. OLAF APPEARS TO BE IN THE PROCESS OF MAKING THE EXPECTED GRADUAL TURN TOWARD THE NORTH AS THE MID-LEVEL HIGH TO ITS NORTH SHIFTS SOUTHEAST AND WEAKENS. TODAY THROUGH THURSDAY THE STEERING PATTERN WILL INCREASINGLY FEATURE A MID-LEVEL HIGH CENTERED EAST OF OLAF...WITH A WEAKER MID-LEVEL RIDGE NORTH OF OLAF EXTENDING EASTWARD FROM A HIGH CENTERED NEAR THE INTERNATIONAL DATE LINE. THIS IS EXPECTED TO IMPART A STEERING MOTION THAT TAKES OLAF TOWARD THE NORTHWEST AND THEN NORTH-NORTHWEST...AS PASSING MID- LATITUDE SHORTWAVE TROUGHS TO THE NORTH ENSURE THAT THE RIDGE NORTH OF OLAF REMAINS WEAK. A MORE SIGNIFICANT BREAK IN THIS RIDGE WILL BEGIN ON FRIDAY...AND CONTINUE INTO THE WEEKEND...DUE TO A STRONGER SHORTWAVE TROUGH APPROACHING FROM THE WEST. AS THIS OCCURS OLAF WILL MOVE NORTH OF THE RIDGE AXIS...AND BECOME EMBEDDED WITHIN THE MID- LATITUDE WESTERLIES...WHICH WILL STEER IT TOWARD THE NORTHEAST. THE OFFICIAL FORECAST TRACK HAS CHANGED LITTLE FROM THE PREVIOUS... AND LIES NEAR THE MIDDLE OF A TIGHTLY CLUSTERED GUIDANCE SUITE THROUGH THE FIRST 72 HOURS. ON DAYS 4 AND 5...A GREATER SPREAD IN THE GUIDANCE IS SEEN...WITH THE OFFICIAL FORECAST CLOSE TO THE TVCN CONSENSUS. THE OFFICIAL TRACK FORECAST TAKES OLAF OVER STEADILY COOLER SSTS...DIMINISHING FROM 29C TODAY TO 26C BY THE END OF THE FORECAST PERIOD. SHEAR IS EXPECTED TO REMAIN RELATIVELY LIGHT OVER THE NEXT 24 TO 36 HOURS...WITH INCREASING SOUTHWESTERLY SHEAR AND DRIER MID-LEVEL AIR ANTICIPATED THEREAFTER. THUS A GRADUAL WEAKENING TREND IN THE SHORT TERM IS EXPECTED TO BE FOLLOWED BY A MORE SIGNIFICANT RATE OF WEAKENING ON DAYS 4 AND 5. THE INTENSITY FORECAST MOST CLOSELY RESEMBLES THE IVCN GUIDANCE...BUT REPRESENTS A BLEND BETWEEN IVCN AND SHIPS ON DAY 5. FORECAST POSITIONS AND MAX WINDS INIT 21/1500Z 11.9N 144.4W 105 KT 120 MPH 12H 22/0000Z 12.7N 145.5W 100 KT 115 MPH 24H 22/1200Z 13.8N 146.4W 95 KT 110 MPH 36H 23/0000Z 14.9N 146.9W 90 KT 105 MPH 48H 23/1200Z 16.4N 147.2W 85 KT 100 MPH 72H 24/1200Z 19.5N 146.9W 75 KT 85 MPH 96H 25/1200Z 22.0N 145.0W 60 KT 70 MPH 120H 26/1200Z 24.6N 143.0W 45 KT 50 MPH $$ FORECASTER BIRCHARD